From the back it kinda looks like a blenny. Do you have a better picture?
It's a goby, and most likely a species of Bathygobius. These gobies are often called frill-fin gobies because the tips of the upper few pectoral-fin ray branches are free from the fin membrane making the upper part of the fin appear frilled. You should be able to see these if you get the fish in the right angle. It's a little hard to be definite on species from the photos, but check out Bathygobius fuscus as a very likely candidate.